Air pollution modelling using a graphics processing unit with CUDA

The Graphics Processing Unit (GPU) is a powerful tool for parallel computing. In the past years the performance and capabilities of GPUs have increased, and the Compute Unified Device Architecture (CUDA) - a parallel computing architecture - has been developed by NVIDIA to utilize this performance in general purpose computations. Here we show for the first time a possible application of GPU for environmental studies serving as a basement for decision making strategies. A stochastic Lagrangian particle model has been developed on CUDA to estimate the transport and the transformation of the radionuclides from a single point source during an accidental release. Our results show that parallel implementation achieves typical acceleration values in the order of 80-120 times compared to CPU using a single-threaded implementation on a 2.33 GHz desktop computer. Only very small differences have been found between the results obtained from GPU and CPU simulations, which are comparable with the effect of stochastic transport phenomena in atmosphere. The relatively high speedup with no additional costs to maintain this parallel architecture could result in a wide usage of GPU for diversified environmental applications in the near future.Comment: 5 figure

Microstructural and Corrosion Properties of Cold Rolled Laser Welded UNS S32750 Duplex Stainless Steel

The main goal of this work was to study the effect of plastic deformation on weldability of duplex stainless steel (DSS). It is well known that plastic deformation prior to thermal cycles can enhance secondary phase precipitation in DSS which can lead to significant change of the ferrite-austenite phase ratio. From this point of view one of the most important phase transformation in DSS is the eutectoid decomposition of ferrite. Duplex stainless steels (DSSs) are a category of stainless steels which are employed in all kinds of applications where high strength and excellent corrosion resistance are both required. This favorable combination of properties is provided by their biphasic microstructure, consisting of ferrite and austenite in approximately equal volume fractions. Nevertheless, these materials may suffer from several microstructural transformations if they undergo heat treatments, welding processes or thermal cycles. These transformations modify the balanced phase ratio, compromising the corrosion and mechanical properties of the material. In this paper, the microstructural stability as a consequence of heat history due to welding processes has been investigated for a super duplex stainless steel (SDSS) UNS S32750. During this work, the effects of laser beam welding on cold rolled UNS S32750 SDSS have been investigated. Samples have been cold rolled at different thickness reduction (\u3b5 = 9.6%, 21.1%, 29.6%, 39.4%, 49.5%, and 60.3%) and then welded using Nd:YAG laser. Optical and electronical microscopy, eddy\u2019s current tests, microhardness tests, and critical pitting temperature tests have been performed on the welded samples to analyze the microstructure, ferrite content, hardness, and corrosion resistance. Results show that laser welded joints had a strongly unbalanced microstructure, mostly consisting of ferritic phase (~60%). Ferrite content decreases with increasing distance from the middle of the joint. The heat-affected zone (HAZ) was almost undetectable and no defects or secondary phases have been observed. Both hardness and corrosion susceptibility of the joints increase. Plastic deformation had no effects on microstructure, hardness or corrosion resistance of the joints, but resulted in higher hardness of the base material. Cold rolling process instead, influences the corrosion resistance of the base material

Calculation of Phase Diagrams of Ternary Reciprocal Molten Salt Mixtures. The System Li+-K+-F--Cl-

In order to calculate phase diagrams of ternary reciprocal molten salt systems, the conformal ionic solution theory and an earlier developed binary ionic-interaction model has been used to derive the excess chemical potentials of the components. A computer program has been developed which delivers data on phase equilibria in the form of tables of liquidus temperatures against the composition of the system. The method of calculation has been applied to the system Li+-K+-F--Cl- and the calculated phase diagram is compared with the experimental one

Microstructural and Corrosion Properties of Cold Rolled Laser Welded UNS S32750 Duplex Stainless Steel

The main goal of this work was to study the effect of plastic deformation on weldability of duplex stainless steel (DSS). It is well known that plastic deformation prior to thermal cycles can enhance secondary phase precipitation in DSS which can lead to significant change of the ferrite-austenite phase ratio. From this point of view one of the most important phase transformation in DSS is the eutectoid decomposition of ferrite. Duplex stainless steels (DSSs) are a category of stainless steels which are employed in all kinds of applications where high strength and excellent corrosion resistance are both required. This favorable combination of properties is provided by their biphasic microstructure, consisting of ferrite and austenite in approximately equal volume fractions. Nevertheless, these materials may suffer from several microstructural transformations if they undergo heat treatments, welding processes or thermal cycles. These transformations modify the balanced phase ratio, compromising the corrosion and mechanical properties of the material. In this paper, the microstructural stability as a consequence of heat history due to welding processes has been investigated for a super duplex stainless steel (SDSS) UNS S32750. During this work, the effects of laser beam welding on cold rolled UNS S32750 SDSS have been investigated. Samples have been cold rolled at different thickness reduction (ε = 9.6%, 21.1%, 29.6%, 39.4%, 49.5%, and 60.3%) and then welded using Nd:YAG laser. Optical and electronical microscopy, eddy’s current tests, microhardness tests, and critical pitting temperature tests have been performed on the welded samples to analyze the microstructure, ferrite content, hardness, and corrosion resistance. Results show that laser welded joints had a strongly unbalanced microstructure, mostly consisting of ferritic phase (~60%). Ferrite content decreases with increasing distance from the middle of the joint. The heat-affected zone (HAZ) was almost undetectable and no defects or secondary phases have been observed. Both hardness and corrosion susceptibility of the joints increase. Plastic deformation had no effects on microstructure, hardness or corrosion resistance of the joints, but resulted in higher hardness of the base material. Cold rolling process instead, influences the corrosion resistance of the base material

The Power of ideology

ix, 557 p.; 23 cm

Jean-Paul Sartre: A Critical Tribute

Jean-Paul Sartre is seventy: what does he mean to us? He is a man who lived half his life in the limelight of extreme notoriety. An intellectual who already in 1945 had to protest against attempts aimed at institutionalizing the writer, turning his works into 'national goods', exclaiming: 'it is not pleasant to be treated in one's life-time as a public moment.' What must be equally unpleasant is to be constantly subjected to abuse. And the fact is that no writer in his life-time has been the target of so many attacks, from the most varied and rather powerful quarters, as Jean-Paul Sartre. What are the reasons? How should we approach the work of this man: our contemporary

Ideology and Social Science

This paper constitutes one of the early chapters of a study which deals with the fundamental structural features of the various forms of ideology-from religious and moral discourse to politics and to art-taken individually as well as in their manifold interconnections; with the material and social conditions and mechanisms that determine the emergence and subtle transformations of particular ideologies; with the complex instruments and institutions required to secure the more or less enduring impact of ideological systems; and, last but not least, with the intricate relationship between ideology and social science considered both as specific modes of discourse and as determinate social complexes which fulfill a multiplicity of important functions in the global framework of social practice

Alienation and Social Control

In the deeply moving final pages of one of his last works Isaac Deutscher wrote : "the technological basis of modern society, its structure and its conflicts are international or even universal in character; they tend towards international or universal solutions. And there are the unprecedented dangers threatening our biological existence. These, above all, press for the unification of mankind, which cannot be achieved without an Integrating principle of social organization. . . . The present ideological deadlock and the social status quo can hardly serve as the basis either for the solution of the problems of our epoch or even for mankind's survival. Of course, it would be the ultimate disaster if the nuclear superpowers were to treat the social status quo as their plaything and if either of them tried to alter it by force of arms. In this sense the peaceful co-existence of East and West is a paramount historic necessity. But the social status quo cannot be perpetuated. Karl Marx speaking about stalemates in past class struggles notes that they usually ended 'in the common ruin of the contending classes'. A stalemate indefinitely prolonged and guaranteed by a perpetual balance of nuclear deterrents, is sure to lead the contending classes and nations to their common and ultimate ruin. Humanity needs unity for its sheer survival; where can it find it if not in socialism?" Isaac Deutscher concluded his work by passionately stressing : "de nostra res agitur" : it all is our own concern. Thus it seems to me right to address ourselves on this occasion to some of the vital problems which stood at the centre of his interest towards the end of his life